The experimentally established pharmacological role of glucagon as a modifier of hepatic regeneration will be tested for physiological significance by determining the glucagon levels that are found in a rat during the period of hepatic regeneration following partial hepatectomy. The effects of glucagon on hepatic regeneration in the portally eviscerated rat will be determined at different levels of glucagon supplementation with monitoring of these levels by use of a radioimmunoassay. DNA synthesis rates will be determined in rats that are deprived of portal organs, partially hepatectomized and have undergone arterialization of the livers. This will define the role of hepatic blood flow augmentation in the animal with a defined and modifiable status in regard to portal factors.